Nest Boxes for Native Cavity Nesting Birds”

Ecology Technical Bulletin, Number 1 “Nest Boxes for Native Cavity Nesting Birds” Populations of native cavity nesting birds have been in long-term decline throughout New York State, and across the country. Loss of suitable nesting sites and competition from non-native birds are the major factors in these population declines. The New York State Department of Transportation (NYSDOT), through it’s ownership of approximately 1% of New York State, has the potential to enhance nesting opportunities for native cavity nesting birds by the well-thought-out placement of nest boxes. However, it is critical that the decision to place nest boxes be carefully planned so that boxes are of the appropriate type, placed in suitable habitat and are monitored on a regular basis during the nesting season. Failure to consider these factors will result in enhancing nesting opportunities for non-native birds and thus further the plight of our native species. This bulletin will provide basic information and recommendations regarding the proper use of nest boxes on and adjacent to NYSDOT property. For more information, please refer to the references at the bottom on this document. Eastern Bluebird (Sialia sialis) New York’s official state bird, the Eastern Bluebird, historically nested in suitable natural cavities (holes or hollows in trees or wooden fence posts) or cavities excavated by other bird species that offer protection from predators, competitors and the elements. In addition, these nest sites had to be the correct size and needed to be located in the appropriate habitat for bluebirds, i.e. short-grass fields or large mowed areas with scattered shrubs for perching. Natural History - Eastern Bluebirds are usually monogamous and usually mate for life. Bluebirds will usually have 2 nests per year with a first nesting period from mid-March through May and a second nesting period in June - July. The typical clutch consists of 3-5 eggs which are incubated for 14 days with the young fledging (leaving the nest) in 17 days after hatching. The breeding territory for bluebirds ranges from 2-25 acres with one bluebird pair rarely nesting within 300 feet of another bluebird pair. Locating a Bluebird Nest Box - Bluebird nest boxes must be placed in the proper habitat, be solidly constructed, be mounted correctly and be monitored regularly if they are to attract and be successfully utilized by bluebirds or other native cavity nesting birds. Bluebirds prefer to nest in areas that do not have concentrated human activity and that contain large lawns or other mowed areas with short grasses and a scattering of shrubs or saplings nearby for perching. Tall grasses discourage bluebird use as bluebirds have difficulty locating and capturing food (grasshoppers) in the thick cover. Even in good habitat, bluebirds are discouraged from nesting within urban areas (competition with starlings and house sparrows), within 50 feet of well-used pedestrian areas or highways, within 50 feet of woods or brush (competition from house wrens), within 100 feet of buildings (competition from starlings and house sparrows), in 1 heavily shaded areas, near water (competition from tree swallows) or within 300 feet of another bluebird nest. Bluebird boxes should be mounted on a smooth steel pipe (to discourage climbing predators) and placed 5-6 feet above the ground (to facilitate monitoring) with the entrance hole facing away from the direction of the prevailing weather (usually to the east). Selecting a Bluebird Nest Box Design - There are two basic types of bluebird nest box designs to choose from - the Standard or Duncan Box and the Peterson Box. Bluebirds will readily accept either box, however the larger, more expensive and more difficult to construct Peterson has been shown to be slightly better in attracting bluebirds. Regardless of which design is chosen, it is critical that the box retain the following features: 1. Properly sized and placed entrance hole; 2. Adequate ventilation; 3. Adequate drainage; 4. No pressure-treated lumber, 5. No dark colored paints of stains; 6. A minimum front roof overhang of 5 inches; and 7) no external perch placed on the front of the box. Monitoring a Bluebird Nest Box - If prior arrangements are not made to monitor the nest box at least once per week during the nesting period, then DO NOT install the box. The New York State Bluebird Society and/or local birding and conservation groups can usually assist with monitoring efforts. Failure to frequently monitor nest boxes can actually hurt bluebird populations by increasing nesting success of aggressive non-native cavity nesting competitors, such as house sparrows and starlings. In addition, nest box monitoring provides important biological information regarding the status of bluebirds. At a minimum, nest boxes should be checked once per week during the nesting season (mid-March thru August) to check for nesting activity. If a house sparrow or starling nest is found, it should be immediately removed (this is legal as these species are unprotected). If a bluebird, tree swallow or house wren nest is found the box should be monitored sufficiently to determine: 1. Dates for egg laying, hatching and fledging; 2. Number and color of eggs (usually 95% blue and 5% white); 3. Number of chicks hatched; 4. Number of chicks fledged; 5. Any indicators of nest failure; and 6. Any evidence of blowflies, ants or wasps. After each nesting attempt, all nest material should be removed from the box to enhance subsequent nesting opportunities. The old nest material should be removed from the vicinity of the box to avoid attracting predators to the nest box. Bluebird Competitors - Several species of birds compete with bluebirds for the use of nest boxes; some of these competitors are beneficial while others should be strongly discouraged as inadvertently increasing their numbers will actually hurt bluebird populations. Tree Swallows are migratory, beneficial, native cavity nesters that often utilize “bluebird” nest boxes. Tree swallows eat many biting insects, do not kill bluebirds and usually don’t arrive on the nesting grounds until after bluebirds have had a chance to establish a nesting territory. Tree swallows will nest “side-by-side” with bluebirds, however will drive away any other tree swallows within their nesting territory, therefore placing 2 boxes in tandem (10 to 15 feet apart) will allow nesting opportunities for both species. House Wrens and Black-capped Chickadees are also native cavity nesters that will use nest boxes. These species will not compete directly with bluebirds when box location is appropriate and, like tree swallows, will not kill or drive-off bluebirds. House wren use of nest boxes can be avoided by not placing boxes in or within 50 feet of brushy 2 areas or hedge rows. Black-capped chickadees are not significant users of nest boxes, however their use seems to be greater when boxes are placed on trees or in or within 50 feet of forested areas. House Sparrows are resident, non-native cavity nesters imported from Europe in the 1800's and represent the greatest threat to our native cavity nesting song birds. House sparrows do not migrate, so they are often the first to claim any available nest boxes. House sparrows are also extremely aggressive and will drive-off other birds that have started nesting in a box (there are many reports of house sparrows killing adult and nestling bluebirds in boxes!). The best way to avoid house sparrow competition is to NOT place boxes in urban areas, within 100 feet of any buildings (especially barns) and to monitor boxes at least once/week during the nesting period and remove any house sparrow nests (this is legal). Failure to prevent house sparrows from successfully rearing young in nest boxes is more harmful to bluebirds than not putting-up any boxes at all! European Starlings are also non-native cavity nesters that were inadvertently introduced into the US in the 1800's, however since starlings are larger than bluebirds, having the correct size entrance hole will prevent starlings from entering the nest box (1 ½ inch diameter round hole or 2 3/4 inch by 1 3/8 inch oval hole). Bluebird Predators - Raccoons are a significant predator of bluebird nest boxes, however they can be deterred from reaching into the box by having the roof over-hang at least 3 inches over the front of the box. In addition, all bluebird nest boxes should be equipped with adequate predator guards to deter house cats (yes, your feline pets kill millions of songbirds annually), raccoons, climbing snakes, etc. that quickly adapt to obtaining an easy meal at unprotected boxes. American Kestrel (Falco sparverious) The American Kestrel, or Sparrow Hawk, is the smallest North American falcon and is dependant on the existence of natural tree cavities or artificial nest boxes for nesting sites. These colorful predatory birds (raptors) are the smallest cousin of the Peregrine Falcon and are frequently seen perched or “hovering” along New York’s highways, especially the interstates. Kestrels are beneficial members of the ecological community primarily for the large numbers of rodents and insects that they consume on a daily basis. Although kestrels will occasionally consume small birds, their normal diet consists of meadow voles, deer mice, shrews and large insects such as grasshoppers and katydids. Natural History - Kestrels belong to the falcon order and are classified as raptors or bird of prey. Raptors are roughly characterized by the presence of a hooked beak, sharp talons, large, forward-facing eyes and a predatory life style. Kestrels begin nesting in late March by locating a suitable natural tree cavity, an unused nest cavity excavated by a pileated woodpecker or an artificial nest box. Kestrels usually lay 5 eggs (1 per day) that are white, pinkish-white or cinnamon in color and uniformly covered with small brown spots.

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